Bad data, ‘ghost triggers’ set off false earthquake alert, seismic expert says
Faulty transmissions of data caused the false earthquake alert sent to communities across Northern California Thursday, said a seismic expert with the early warning project.
The issue was what Angie Lux, an earthquake early warning scientist at Berkeley Seismological Laboratory, called “gappy data”: erratic bursts of data sent by sensors scattered across the Nevada landscape that confused seismologists’ algorithms.
The algorithms processed the information as seismic activity coming from the areas where the sensors were located, Lux said. The data caused “ghost triggers” that set off the early morning alert across a wide swath of California through the MyShake and ShakeAlert apps, which carries earthquake early warnings, and the Wireless Emergency Alert system that buzzes cellphones.
“That’s what caused it to create that event,” Lux said Friday, calling it a “very unusual situation.”
The alert, issued just after 8 a.m. Thursday, mistakenly claimed a magnitude 5.9 earthquake had struck near Carson City, Nevada.
The alert was canceled within an hour, and the USGS later posted a notice to its main earthquakes page, saying that the event did not occur, and had been deleted from USGS websites and data feeds while the federal agency worked to understand the cause of the false alarm.
Lux is a project scientist who works on the EPIC algorithm and the ShakeAlert system managed by the U.S. Geological Survey. “It’s something we’ve never seen before and hope we’ll never see again.”
EPIC, or Earthquake Point‐Source Integrated Code, algorithms calculate temblor magnitudes in real time. The algorithms are used in concert with early warning systems to provide communities with several seconds’ notice before major shaking events occur.
Lux said scientists have shut down the sensors that sent the faulty data and are working to “make sure the algorithm is more robust.”
“By the end of the day, we understood what happened: it’s a data issue,” Lux said. “We’re digging in a little more to make sure that that won’t happen again.”
Christie Rowe, director of the Nevada Seismological Laboratory, said Thursday that the early warning system had issued 160 correct alerts, three false ones and missed 14 quakes since it launched in California about six years ago. The system also covers Oregon and Washington.
This story was originally published December 5, 2025 at 3:17 PM.
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